In Mongolia, a Central Asian lower-middle income country, intensive care medicine is an under-resourced and-developed medical specialty. The burden of critical illness and capacity of intensive care unit (ICU) services in the country is unknown. In this nationwide census, we collected data on adult and pediatric/neonatal ICU capacities and the number of ICU admissions in 2014. All hospitals registered to run an ICU service in Mongolia were surveyed. Data on the availability of an adult and/or pediatric/neonatal ICU service, the number of available ICU beds, the number of available functional mechanical ventilators, the number of patients admitted to the ICU, and the number of patients admitted to the study hospital were collected. In total, 70 ICUs with 349 ICU beds were counted in Mongolia (11.7 ICU beds/100,000 inhabitants; 1.7 ICU beds/100 hospital beds). Of these, 241 (69%) were adult and 108 (31%) pediatric/neonatal ICU beds. Functional mechanical ventilators were available for approximately half of the ICU beds (5.1 mechanical ventilators/100,000 inhabitants). While all provincial hospitals ran a pediatric/neonatal ICU, only dedicated pediatric hospitals in Ulaanbaatar did so. The number of adult and pediatric/neonatal ICU admissions varied between provinces. The number of adult ICU beds and adult ICU admissions per 100,000 inhabitants correlated (r = 0.5; p = 0.02), while the number of pediatric/neonatal ICU beds and pediatric/neonatal ICU admissions per 100,000 inhabitants did not (r = 0.25; p = 0.26). In conclusion, with 11.7 ICU beds per 100,000 inhabitants the ICU capacity in Mongolia is higher than in other low- and lower-middle-income countries. Substantial heterogeneities in the standardized ICU capacity and ICU admissions exist between Mongolian provinces. Functional mechanical ventilators are available for only half of the ICU beds. Pediatric/neonatal ICU beds make up one third of the national ICU capacity and appear to meet or even exceed the demand of pediatric/neonatal critical care.